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<H2>mismatch()</H2>
<P><B>Module:</B>&nbsp;&nbsp;Standard C++ Library&nbsp;&nbsp;&nbsp;<B>Library:</B>&nbsp;&nbsp;<A HREF="2-9.html">Algorithms</A></P>

<PRE><HR><B><I>Function</I></B><HR></PRE>

<UL>
<LI><A HREF="#sec1">Local Index</A></LI>
<LI><A HREF="#sec2">Summary</A></LI>
<LI><A HREF="#sec3">Synopsis</A></LI>
<LI><A HREF="#sec4">Description</A></LI>
<LI><A HREF="#sec5">Complexity</A></LI>
<LI><A HREF="#sec6">Example</A></LI>
<LI><A HREF="#sec7">Standards Conformance</A></LI>
</UL>
<A NAME="sec1"><H3>Local Index</H3></A>
No Entries
<A NAME="sec2"><H3>Summary</H3></A>
<P>Algorithm that compares elements from two sequences and returns a pair of iterators pointing to the first two elements that don't match each other</P>
<A NAME="sec3"><H3>Synopsis</H3></A>

<PRE>#include &lt;algorithm&gt;

namespace std {
  template &lt;class InputIterator1, class InputIterator2&gt;
  pair&lt;InputIterator1,InputIterator2&gt;
  mismatch(InputIterator1 start1, InputIterator1 finish1,
           InputIterator2 start2);

  template &lt;class InputIterator1, class InputIterator2,
            class BinaryPredicate&gt;
  pair&lt;InputIterator1, Inputiterator2&gt;
  mismatch(InputIterator1 start1, InputIterator1 finish1,
           InputIterator2 start2,
           BinaryPredicate binary_pred);
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P>The <SAMP>mismatch()</SAMP> algorithm compares members of two sequences and returns two iterators (<SAMP>i</SAMP> and <SAMP>j</SAMP>) that point to the first location in each sequence where the sequences differ from each other. <SAMP>mismatch()</SAMP> assumes that the second sequence has at least as many members as the first sequence. If the two sequences are identical, <SAMP>mismatch()</SAMP> returns a pair of iterators that point to the end of the first sequence and the corresponding location at which the comparison stopped in the second sequence.</P>
<P>The first version of <SAMP>mismatch()</SAMP> checks members of a sequence for equality, while the second version lets you specify a comparison function object. The comparison function object must be a binary predicate.</P>
<P>The iterators <SAMP>i</SAMP> and <SAMP>j</SAMP> returned by <SAMP>mismatch()</SAMP> are defined as follows:</P>

<UL><PRE>j  == start2  +  (i  -  start1)
</PRE></UL>
<P>and <SAMP>i</SAMP> is the first iterator in the range <SAMP>[start1, finish1)</SAMP> for which the appropriate one of the following conditions hold: </P>

<UL><PRE>!(*i  ==  *(start2  +  (i  -  start1)))
</PRE></UL>
<P>or</P>

<UL><PRE>binary_pred(*i, *(start2 + (i - start1))) == false
</PRE></UL>
<P>If all of the members in the two sequences match, <SAMP>mismatch()</SAMP> returns a pair of <SAMP>finish1</SAMP> and <SAMP>start2 + (finish1 - start1)</SAMP>. </P>
<A NAME="sec5"><H3>Complexity</H3></A>
<P>At most <SAMP>finish1 - start1</SAMP> applications of the corresponding predicate are done.</P>
<A NAME="sec6"><H3>Example</H3></A>

<UL><PRE>//
//  mismatch.cpp
//

#include &lt;algorithm&gt;    // mismatch
#include &lt;functional&gt;   // less_equal
#include &lt;iostream&gt;     // cout, endl
#include &lt;utility&gt;      // pair
#include &lt;vector&gt;       // vector



int main ()
{
    typedef std::vector&lt;int, std::allocator&lt;int&gt; &gt; Vector;
    typedef Vector::const_iterator                 Iter;

    const Vector::value_type d1[] = { 1, 2, 3, 4 };
    const Vector::value_type d2[] = { 1, 3, 2, 4 };

    // Set up two vectors.
    const Vector vi1 (d1 + 0, d1 + sizeof d1 / sizeof *d1);
    const Vector vi2 (d2 + 0, d2 + sizeof d2 / sizeof *d2);

    // p1 will contain two iterators that point to 
    // the first pair of elements that are different 
    // between the two vectors.
    std::pair&lt;Iter, Iter&gt; p1 =
        std::mismatch (vi1.begin (), vi1.end (), vi2.begin ());  

    // Find the first two elements such that an element in 
    // the first vector is greater than the element in
    // the second vector.
    std::pair&lt;Iter, Iter&gt; p2 =
        std::mismatch (vi1.begin (), vi1.end (),
                       vi2.begin (), std::less_equal&lt;int&gt;());

    // Output results.
    std::cout &lt;&lt; *p1.first &lt;&lt; ", " &lt;&lt; *p1.second &lt;&lt; std::endl;
    std::cout &lt;&lt; *p2.first &lt;&lt; ", " &lt;&lt; *p2.second &lt;&lt; std::endl;

    return 0;
}


Program Output:
</PRE></UL>
<UL><PRE>2, 3
3, 2
</PRE></UL>
<A NAME="sec7"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.1.7</I></P>

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